Magnetostrictive transformer



July 19, 1966 H. P. QUINN MAGNETOSTRICTIVE TRANSFORMER Filed March 1l, 1963 fra/7 /vlvl vvvInj INVENTOR. asfy i? Qz//A//v ATTORNE YS United States Patent() 3,261,339 MAGNETOSTRICTIVE TRANSFORMER Halsey P. Quinn, Morris Plains, NJ., assigner to Tung- Sol Electric Inc., a corporation of Delaware Filed Mar. 11, 1963, Ser. No. 264,216 Claims. (Cl. 123-148) This invention relates to a magnetostrictive transformer used in conjunction with an ignition circuit for internal combustion engines. The invention has particular reference to a novel transformer which can be used to transform a low voltage current pulse into a high voltage current pulse produced by an output circuit having a resistance which approximates infinity.

Many ignition circuits have been developed and used for the production of a high voltage spark between the termina-ls of a spark plug installed in the combustion chamber of a gasoline engine. The more useful type of circuits generate a voltage pulse which has a very fast rise time, of the order of a few microseconds, this type of spark being more useful and more dependable than the older type of voltage .pulses generated by the usual output transformer. The circuits described herein are substantially the same as those shown in prior applications filed by the same inventor with the exception that the magnetostrictive transformer has been substituted instead of the usual magnetic core transformer having an input primary winding and an output secondary winding. An input winding is still used but this is applied to a magnetostrictive nickel co-re and the output circuit includes two piezoelectric crystals.

One of the objects of this invention is to provide animproved ignition circuit which avoids one or more of the disadvantages and limitations of prior art arrangements.

Another object of the invention is to transform a low voltage pulse into a high voltage pulse without the use of a secondary winding.

Another object of the invention is to produce an output pulse in an output circuit having only capacitive reactance.

Another object of the invention is to reduce the probability of failure in a system of electrical power transformation by eliminating short circuits and open circuits in a transformer secondary winding.

Another object of the invention is to reduce the cost of transformers.

Another object of the invention is to change the output impedance of a transformer from an inductive reactance to a capacitive reactance.

Another object of the invention is to eliminate direct current leakage through a transformer secondary circuit.

The invention includes an ignition circuit for internal combustion engines having an input circuit which includes the usual source of direct current power, a pair of breaker contacts operated by the engine, and circuit means for generating a series of current pulses. The circuit also includes a transformer having a primary winding wound on a magnetostrictive core and a piar of piezoelectric crystals mechanically secured to a portion of the core. The crystals generate voltage pulses when current pulses are applied to the primary winding. The output circuit includes a storage capacitor connected in series with the primary winding of an output transformer and one of the crystals. The output Icircuit; also includes a discharge means connected across the storage capacitor and the primary winding of the output transformer. The second crystal triggers the discharge device to discharge the storage capacitor and generate the output high voltage pulse which is applied to one of the spark plugs through a distributor.

For a better understanding of the present invention, together with other and further objects thereof, reference is made to the following description taken in connection with the accompanying drawings.

FIG. 1 is a schematic diagram of connections of one form of the ignition circuit using a single transistor in the input portion of the circuit.

FIG. 2 is schematic diagram of connections similar to FIG. 1 but employing two transistors iny the input circuit.

FIG. 3 is a schematic diagram similar to FIG. 1 but employing an additional transformer in the input portion of the circuit.

FIG. 4 is a side view of one form of the magnetostrictive transformer.

FIG. 5 is a side view of another form of magnetostrictive transformer which may be used with the circuit.

Referring now to FIG. 1, a circuit is shown which is similar to one of the circuits (FIG. 2) shown in a patent application Serial No. 70,889, filed November 2l, 1960, now Patent No. 3,131,327 bythe present applicant. The circuit includes a source of direct current potential 10 which may he a storage battery, a pair of breaker points 11 which are operated by the engine, and a transistor 12 which amplifies the current pulse generated by the breaker contacts and applies this pulse to a primary winding 13 wound on a magnetostrictive core 14. The breaker contacts 11 are connected between the negative terminal of battery 10, which may be grounded, and the base of transistor 12 in series with a limiting resistor 15. The collector of transistor 12 is connected to the negative battery -terminal in series with a second limiting resistor 16. The emitter of transistor 12 is connected to the positive terminal of the battery in series with the primary winding 13. Another portion of the primary winding 17 is connected to the negative terminal of the battery in series with a diode rectifier 18, the purpose of which will be explained when the operation of the circuit is described.

The magnetostrictive core 14 is mechanically secured to two piezoelectric crystals 20 and 21, each having an electrode for the transmission of voltage pulses. The crystals 20 and 21 are connected to a storage-discharge circuit which includes a storage capacitor 22, a diode rectifier 23, and the pri-mary winding 24 of an output transformer 25 whose secondary winding 26 is connected through a distributor to a series of spark plugs 28. The rectifier 23, capacitor 22, and winding 24 are all connected in series across crystal 20. In order to discharge the storage capacitor and obtain an output Voltage pulse, a discharge device 30 is connected across the terminals of the series circuit which includes capacitor 22 and primary winding 24. This discharge device may be a gaseous discharge tube, commonly known as a thyratron, or it may be a controlled rectifier 31 shown in dotted lines. If a thyratron is used as shown in full lines in FIG. l, the ring electrode 32 is connected to one of the terminals of crystal 21. If the controlled rectifier 31 is used, its con trol electrode 32A is connected to the same crystal electrode.

The operation of this circuit is as follows: when contacts 11 are open, the emitter-collector electrodes of the transistor 12 pass no current because the transistor is cut off and no current flows through the battery 1t). When contacts 11 are closed, the base of transistor 12 is given a potential which is substantially the same as its collector and then current flows from the ground terminal through the battery 10, through winding 13, through the emitter-collector circuit of transistor 12 and back to ground through resistor 16. The magnetic ilux generated by Winding 13 causes the core 14 to contract a small amount and thereby change the di-mensions of both crystals 20 and 21 and generate an output voltage. This voltage is applied, in the first case, to the series circuit which includes rectifier 23, capacitor Z2, and primary winding 24. The other crystal 21 applies a Voltage between the ground connection and the firing electrode 32 of the discharge device 30. The circuit described above can be employed to re a spark plug 28 when the contacts 11 are closed or when these contacts are opened, the transfer of one condition to another requires only that the potentials of the two crystals be reversed.

If it is desired to send a Spark through the distributor 27 when the contacts 11 are closed, then the crystals are arranged so that current passing through winding 13 contracts the core 14 and generates a positive potential on conductor 33 and a negative potential on conductor 34. The result of this operation is the charging of storage capacitor 22 through the rectifier 23. Next, when the contacts 11 are open the current through winding 13 is abruptly cut off and the core expands to its original size thereby compressing the crystals and generating voltages which make conductor 33 negative and making conductor 34 positive. The positive charge on conductor 34 raises the potential of the firing electrode 32 and the discharge device 30 becomes conductive, discharging the storage capacitor 22 through the primary winding 24, and thereby generating a high voltage on the secondary winding 26 which is applied to one of the spark plugs 28 by distributor 27.

If it is desired to create a spark when the contacts close, the crystals 20 and 21 are reversed so that when the contacts first close, a negative potential is applied to conductor 33 and a positive potential is applied to conductor 34. If this is the initial contact closing, nothing happens because capacitor 22 has not yet been charged. Now, when contacts 11 open, conductor 33 is made positive and the capacitor 22 is charged. At this same time conductor 34 is made negative and the discharge device 30 is maintained in its non-conductive condition. Next, at the second closing of contacts 11, conductor 33 is made negative and conductor 34 is made positive to discharge storage capacitor 22 through device 30 and the primary winding 24. It is obvious from the above description that the circuit may be adapted to any type of breaker program.

During the operation of this circuit sorne excess voltage pulses may be generated which are not helpful to the efficient operation of the system. The diode rectifier 18 is connected between one terminal of battery and one side of primary winding 17. If, for any reason, during the operation of the system capacitor 22 is not discharged, the next current pulse through winding 13 may produce an excessive voltage pulse across windings 13 and 17. Diode 1S limits this pulse and sends the excessive current through battery 10 in a direction which charges it.

The circuit shown in FIG. 2 is the same as that shown in FIG. 1 except that two transistors 12 and 40 are used. A similar circuit has been described in patent application Serial No. 70,889, filed Nov. 2l, 1960, by the present applicant. The action is substantially the same except that the two transistors provide greater current amplification for the current which flows through contacts 11 and therefore this circuit is capable of creating greater output voltages. The same discharge circuit is employed and the same type of magnetostrictive transformer is used.

The circuit shown in FIG. 3 contains the same magnetostrictive transformer and the same output circuit. The input circuit includes a single transistor 41 coupled to the breaker contacts 11 by a transformer 42 having a winding 43 and a split secondary winding 44. This particular type of input circuit has been described in copending application, Serial No. 181,992, filed March 23, 1962, by the applicant. The emitter is connected to the mid-point of winding 44 in series with a diode 46. In this type of input circuit transistor 41 is normally nonconductive when the contacts 11 are open and therefore no current flows from the source of potential 10, through winding 13, diode 46, and the collector-emitter electrodes, to the other side of the battery. When the points close, the transistor is made conductive and current flows through the above-mentioned circuit causing the generation of a magnetic field in core 14 of the input transformer. The rise of current in this circuit is limited by resistor 45. When the contacts are opened, the current through winding 43 is cut off abruptly causing a short current pulse -to flow through winding 13. The start of this current pulse causes a contraction of the core 14 and the cessation of the pulse causes the expansion of the core. Both actions induce voltages in both of crystals 20 and 21. The two portions of secondary winding 44 form a feed-back circuit between the base-emitter electrodes and the collector-emitter electrodes and thereby produce a faster break in the current and a sharper mechanical action applied to the crystals. As explained above, in connection with the operation of the circuit shown in FIG. 1, the circuits in FIGS. 2 and 3 can be arranged to produce a high Voltage pulse at the spark plugs either when the contacts are opened or when they are closed. The only adjustment necessary is the reversal of the crystals 20 and 21 to produce opposite voltages. The action of the output circuit is the same as described above.

One form of transformer 14 is shown in FIG. 5 where a nickel core 14 is surrounded by a winding 13 which causes it to expand and contract. Crystals 20 and 21 are positioned between one end of core 14 and a portion of a ferromagnetic core 47 which may be made of high permeability iron laminations. In this type of construction the nickel core 14 and the crystals 20 and 21 must be pre-stressed and maintained in a compressed condition. Then when current is applied to winding 13 a portion of the stress is relieved and the crystals generate a voltage. When the current through winding 13 is removed the crystals and the core return to their former stressed condition.

The transformer arrangement shown in FIG. 4 includes two nickel cores 14A and 14B surrounded by windings 13A and 13B. The cores are connected at their end points with transverse ferromagnetic cores 48 and 49. In this arrangement the crystals 20 and 21 are not pre-stressed but are held securely between extensions of the two iron cross pieces. When current is sent through windings 13A and 13B the nickel cores 14A and 14B contract and pressure is applied to the crystals by the two iron cross pieces. When current is cut off through the windings the cores and crystals return to their natural state.

From the above description it will be evident that the magnetostrictive transformer can be used in ignition circuits to provide a spark either on the making of a pair of contacts or when the contacts are broken.

The foregoing disclosure and drawings `are merely illustrative of the principles of this invention and are not to be interpreted in a limiting sense. The only limitations are to be determined from the scope of the appended claims.

It is claimed:

1. An ignition circuit for internal combustion engines comprising; an input circuit including a source of direct current, a pair of breaker contacts, and circuit means for generating a series of current pulses; a transformer which includes a winding on a magnetostrictive core and a pair of piezoelectric crystals mechanically coupled to a portion of said core, said `winding having its terminals connected to said input circuit for receiving said current pulses; an output circuit including La storage capacitor connected in series with a primary winding of an output transformer and a rectifier; said output circuit connected across one of said crystals for charging the capacitor during a charging interval; and a discharge device connected across said capacitor and said primary winding for discharging the capacitor through the primary winding during a discharge interval, said discharge device coupled to the other crystal for initiating the discharge.

2. An ignition circuit for internal combustion engines comprising; an input circuit including a source of direct current power, a pair of breaker contacts, and circuit means for generating a series of current pulses ywhen the breaker contacts are opened `and closed; a transformer which includes a winding on 1a magneostrictive core and a pair of piezoelectric crystals mechanically coupled to a portion of the core; said winding having its terminals connected to said input circuit for receiving current pulses; and output circuit connected to both of said crystals, said output circuit including a storage capacitor, a rectifier, and a primary winding of an output transformer con nected in series; said output circuit connected across `one of said crystals for charging the capacitor during a charging interval; said youtput circuit also including a -gaseous discharge device connected across said capacitor and said primary winding for discharging the capacitor through the primary winding during `a discharge interval; and coupling means between said discharged device and the other of said crystals for initiating the discharge.

3. An ignition circuit for internal combustion engines comprising; an input circuit including a source of direct current power, `a pair of breaker contacts which open and close in synchronism with a portion of the engine, and circuit means for generating a series of current pulses when the breaker contacts are opened and closed, said circuit means including a transistor for amplifying the current pulses produced by said contacts; a transformer which includes a Winding on a magnetostrictive core and a pair of piezoelectric crystals mechanically coupled to said core; said ywinding having its terminals connected to the input circuit for receiving the input pulses; an output circuit connected to both of said crystals, said output circuit including a storage capacitor, a rectifier, and a primary winding of an output transformer connected in series; said output circuit connected across one of said crystals for charging the capacitor during .a charging interval; said output circuit also including a gaseous discharge device connected across said capacitor and said primary Winding for discharging the capacitor through the primary Winding during a discharge interval; and coupling means between said discharge device and the other of said crystals for initiating the discharge.

4. An ignition circuit as claimed in claim 3 wherein said core is made of nickel.

5. An ignition circuit as claimed in claim 3 wherein said input circuit contains two transistors, each for amplitying the current pulses generated by the breaker contacts.

6. An ignition circuit as claimed in claim 3 wherein said crystals are poled so as to charge the storage capacitor when the breaker contacts close anad to discharge the storage capacitor when the breaker contacts open.

7. An ignition circuit as claimed in claim 3 wherein said crystals are poled so as to charge the storage capacitor when the breaker contacts open and to discharge the storage capacitor when the breaker contacts close.

S. An ignition circuit as claimed in claim 3 wherein said magnetostrictive core is an elongated metal rod with said crystals mounted adjoining one of the rod'ends and the core and crystal assembly is secured within a shell of ferromagnetic material.

9. An ignition circuit as claimed in claim 3 whereiny said magnetostrictive core is divided into two parts, each forming a leg on a three-legged core assembly, said crystals being a part of the third leg.

10. An ignition circuit as claimed in claim 9 wherein said transformer includes three legs and two cross pieces, secured together to form a unitary structure, said crystals forming a part of a central leg under the influence of the expansion and contraction of the other two legs.

No references cited.

MARK NEWMAN, Primary Examinez'.

L. M. GOODRIDGE, Assistant Examiner. 

1. AN IGNITION CIRCUIT FOR INTERNAL COMBUSTION ENGINES COMPRISING; AN INPUT CIRCUIT INCLUDING A SOURCE OF DIRECT CURRENT, A PAIR OF BREAKER CONTACTS, AND CIRCUIT MEANS FOR GENERATING A SERIES OF CURRENT PULSES; A TRANSFORMER WHICH INCLUDES A WINDING ON A MAGNETOSTRICTIVE CORE AND A PAIR OF PIEZOELECTRIC CRYSTALS MECHANICALLY COUPLED TO A PORTION OF SAID CORE, SAID WINDING HAVING ITS TERMINALS CONNECTED TO SAID INPUT CIRCUIT FOR RECEIVING SAID CURRENT PULSES; AN OUTPUT CIRCUIT INCLUDING A STORAGE CAPACITOR CONNECTED IN SERIES WITH A PRIMARY WINDING OF AN OUTPUT TRANSFORMER AND A RECTIFIER; SAID OUTPUT CIRCUIT CONNECTED ACROSS ONE OF SAID CRYSTALS FOR CHARGING THE CAPACITOR DURING A CHARGING INTERVAL; AND A DISCHARGE DEVICE CONNECTED ACROSS SAID CAPACITOR AND SAID PRIMARY WINDING FOR DISCHARGING THE CAPACITOR THROUGH THE PRIMARY WINDING DURING A DISCHARGE INTERVAL, SAID DISCHARGE DEVICE COUPLED TO THE OTHER CRYSTAL FOR INITIATING THE DISCHARGE. 